Treatment of cellulose



Patented Sept. 5, 1950 I I 2,521,446. TREATMENT OF onLLULosE Howard M.Buckwalter, Detroit, and Phillip D.

Montgomery, Oak Park, Mich., assignors to 1 United States RubberCompany, New York; N. Y., a corporation of New Jersey No Drawing.Application January 11, 1950, Serial No. 138,068

8 Claims.

This invention relates to the protection of native and regeneratedcellulose fibers against deterioration by heat aging.

Deterioration of cellulose fiber upon subjection to elevatedtemperatures for prolonged periods of time is a very serious problem inthe art. This problem is encountered particularly in the case of rubberarticles which are reinforced with cellulose fiber, almost invariablystranded and in the form of cords or fabric, which may be a woven fabrichaving warp and woof threads or a so-called weftless fabric or webfabric composed of parallel cords joined together by a dry deposit ofrubber latex, as described for example in the patent to Hopkinson, No.1,424,020. Such cellulose fiber reinforced articles include pneumatictires, steam hose, power transmission belts, conveyor belts, etc. Thesearticles are subjected to levated temperatures in normal use, either becuse they are subjected to external heating, or because they generateheat within themselves by reason of repeated rapid flexing, as in thecase of pneumatic tires. The deterioration of the reinforcing cellulosefiber under the action of heat is particularly evidenced by progressivereduction in tensile strength of the fiber, leading to eventualbreakage. This deteriorating action of prolonged heating on cellulosefibers is a principal cause of failure of such articles as pneumatictires and steam hose.

The principal object of the present invention is to provide an improvedmethod of protecting cellulose fiber, especially when stranded and inthe form of a fabric, against deterioration by heat aging. Anotherobject is to provide articles of manufacture embodying cellulose fibersprotected against heat deterioration, such articles of manufactureincluding cellulose fibers themselves, whether unstranded, stranded, orin the form of fabric, and vulcanized rubber articles reinforced withsuch cellulose fibers, such as pneumatic tire casings reinforcedtherewith. Other objects of the invention will more fully hereinafterappear.

According to the present invention, cellulose fiber is protected againstdeterioration by heat aging by treatment with guanazole, sometimes'fective chemical in imparting to cellulose fibers the ability towithstand deterioration by the acknown as the tautomer of3,5-diamino-1,2,4-

triazole. Guanazole has the structural formula NH.NH

have found that guanazole is a remarkably eftion of heat over extendedperiods of time.

In carrying out the invention, the guanazole may be applied to thecellulose fiber in any suitable manner, conveniently by immersing thefiber to be treated in a solution or dispersion of the guanazole foratime suflicient for the fiber to become substantially impregnated withthe guanazole solution. The cellulose fiber employed is usually ordinarygrey cotton fiber although the process of the invention may also beemployed advantageously with the various regenerated cellulose fibers,such as viscose rayon. The invention is applicable to native cellulosefibers in general, such as fiax, hemp, etc., as well as to scoured,bleached and mercerized cotton. In place of immersing the fiber in thetreating solution, we may incorporate the g'uanazole in the fiber in anyother suitable manner, such as by spraying or brushing.

For convenience, we usually employ the guanazole in the form of anaqueous solution, typically at a concentration of from 1 to 15% byweight, although marked improvement in heat age resistance is alsoobtainable with surpris- 'ingly dilute solutions, e. g., solutionscontaining 0.5% of guanazole. If desired, more concentrated solutionsmay be employed, e. g., a 15 to 25% solution, although there isordinarily only minor advantage in using solutions more concentratedthan about 15%. Organic solvents, e. g. alcohol, may be substituted forthe water if desired.

The treatment with guanazole may be carried out at room temperature, orat elevated temperatures, for example, up to the boiling point of theaqueous solution. The time of contact between the cellulose fiber andthe guanazole solution should be sufllcient to permit substantialpenetration of the fiber. Usually treatment times of from 30 seconds to2 minutes at the boiling point are adequate for this purpose, althoughlonger treatment times are without adverse effect and may be employed ifdesired.

In order to obtain the benefits of the treatment of this invention it isnecessary that the guanazole remain in the cellulose fiber and beactually present in the fiber at the time the fiber is subjected to theheating which would ordinarily cause deterioration. I have found thatguanazole present in the cellulose fiber in amount of at least 0.25% onthe weight of the fiber, and usually in amount of from 0.5% to 7%, iseffective to produce substantial improvement in the heat age resistanceof the fiber. Larger amounts 3 than 7%, e. g. 10% or more, may be usedif desired, but are generally unnecessary.

The following examples will illustrate the practice of my invention inmore detail.

EXAMPLE 1 Samples of grey (native) cotton tire cord and viscose rayontire cord were immersed in hot (95 to 100 C.) aqueous solutions ofguanazole of 1% to 10% concentration for 2 minutes, as indicated inTable 1 below. The cord was then removed from the solution, and theexcess solution was allowed to drain off the cord. The cord was thendried at 110 C. The cord was thereafter aged in the air at a temperatureat 165 C. for 72 hours. This procedure is known as open heat aging. The165 C. aging temperature is considerably in excess of the temperature atwhich. cotton cord ordinarily suffers-serious progressive irreversibleloss of tensile strength due to chemical deterioration of the cotton bythe action of thefiheat, namely 125 C. After such aging the te silestrength of the treated cord was determined at 70 F. and 60% relativehumidity, and the results obtained were compared to control samples asindicated in Table 1.

tube and subjected to heat aging for 72 hours at 165 C., following whichthe tube was broken r stantially impervious rubber. Under sealed heataging conditions, the improvement obtained was excellent both on rayonand cotton.

The foregoing examples show that the heat stabilizing activity of theguanazole increases with advancing concentrations of the aqueoussolutions from which it is applied and hence is a direct function of theamount deposited on the cellulose. Results equal to those shown in theexamples are obtained with a treating (immersing) time of thirty secondsat 100 0., or for longer periods of time at temperatures below 95"-Table i.E17ect of guwnazole on th open heat aging resistance of nativecotton and viscose rayon tire cord Period of Cotton Rayon Concentrationof Guanazole In 3? Aqueous Treating solmm Aging at Tensile RelativeTensile 252; Relative 165 0. Strength Retained Strength StrengthRetained Strength Hours Lbs. Per cant I Lbs. Per cent 0 per cent 0 16-6100 21. 0 100 0 per cent. 72 6. 0 36 100 8. 7 42 100 l per can 72 10. 261 171 8. 41 98 3 per cent. 72 12. 3 74 207 9. 0 43 103 5 per cent. 7212. 9 78 216 ll. 1 63 l28 per cent 72 13- 2 80 222 12. 5 59 143 Table2.Efiect of guanazole on the sealed tube heat aging resistance of nativecotton and viscose rayon tire cord Period of 9" Concentration oi'Guanazo le In g Aqueous Tmatmg mm Aging at Tensile Relative Tensile gggg Relative 165 0. Strength Retained Strength Strength RetainedStrength Hours Lbs. Per cent Lou. Per cent 0 per cent 0 16. 6 100 21. 0100 0 per cent 7 5. 2 3 100 4. 6 22 100 10 per cent 7 14- 4 87 278 16. 880 366 EXAMPLEZ Grey cotton tire cord and viscose rayon tire cord weretreated with aqueous guanazole solutions of varying concentration fortwo minutes at 95 to 100 C. in the same manner as in Example 100 C. Inall cases it is desirable that the treating conditions be such as toeflect the deposition of at least 0.25%, and preferably at least 0.5% ofguanazole in the cellulose. When water is the solvent, solutionscontaining 1 to 15% of guanazole result in deposition of 0.5% to 7% ofthe material in the cellulose.

The guanazole used in these examples was prepared by the method ofStolle and Krauch (ibid.).

- The material was recrystallized from water in the form of whiteanisotropic crystals melting at 205-7" 0. It is not essential forpurposes of this invention that the product be purified byrecrystallization. Good results are obtained using the crude material,after removing the excess reactants.

1.. The cords were similarly drained, dried, and

thereafter subjected to sealed heat aging conditions, that is, the cordswere sealed in a, glass From the foregoing it is evident that theinvention provides a method of treating cellulose fibers, whether greycotton fibers or other forms of cellulose fiber such as regeneratedcellulose. whether in the form of fibers as such, or as yarn, cord orfabric, whereby the resistance of the fiber to the deteriorating effectof prolonged exposure to elevated temperature is substantially enhanced.Thus, the improved cellulose fibers of this invention containingguanazole are capable of improved serviceability especially whenemployed for such purposes as reinforcing tires, steam hose, and similarrubber-fabric composite articles which normally have a limited servicelife because of the deteriorating action of heat on the fiberreinforcement therein.

The guanazole treated fiber can be encased in rubber which may besubsequently vulcanized at elevated temperatures to a dense, strongproduct without any adverse efiects due to the presence of theguanazole. This is in contrast to certain other chemicals previouslyproposed for improving the heat age resistance of rayon tire cords andthe like, but which are impractical because they decompose atvulcanizing temperatures with liberation of gases, causing blowing inthe tire carcass assembly. Because the guanazole is comparatively stableat vulcanizing tem- Having thus described our invention. what we claimand desire to protect by Letters Patent is:

peratures it retains its chemical identity and re- 7 mains in the fiber,and is available for protecting the fiber on subsequent exposure of thevulcanized articles to high temperature conditions over extended periodsof service.

The guanazole is not decomposed or removed by temperatures ordinarilyemployed in drying or baking tire cord after the cord, usually in theform of a web fabric, has been treated with rubber latex compositions.

While we have described our invention with particular reference to apreferred treatment of cellulose fibers intended to be used forreinforcing rubber articles, it will be understood that the improvedguanazole-containing cellulose fibers of this invention are susceptibleof many other uses where resistance to heat is a desirablecharacteristic. However, the improved cellulose fibers containingguanazole are especially adapted to production of vulcanizedrubber-fabric composite articles, because the guanazole has nodeleterious effect on the vulcanization, and resists vulcanizingtemperatures, thereby resulting in improved vulcanized rubber-fabriccomposite articles.

1. The method of improving the resistance of cellulose fibers to thedeteriorating effects of heat aging which comprises incorporatingguanazole in the cellulose fiber in amount of at least 0.25% by weight.

.2. The method of improving the resistance of cellulose fibers to thedeteriorating effects of heat aging which comprises impregnating thefibers with an aqueous solution containing at least 0.5% by weight ofguanazole.

3. The method of improving the resistance of grey cotton fibers tothedeteriorating effect 01' heat aging which comprises impregnating thegrey cotton fibers with an aqueous solution containing at least 0.5% byweight of guanazole.

4. The method of improving the resistance of regenerated cellulosefibers to the deteriorating effect of heat aging which comprisesimpregnating the regenerated cellulose fibers with an aqueous solutioncontaining at least 0.5% by weight of guanazole.

5. A cellulose fiber characterized by improved resistance to thedeteriorating effect of heat aging containing at least 0.25% by weightof uanazole.

6. A grey cotton fiber characterized by improved resistance to thedeteriorating eflect of heat aging containing at least 0.25% by weightof uanazole.

'7. A rayon fiber characterized by improved resistance to thedeteriorating effect of heat aging containing at least 0.25% by weightof guanazole.

8. A vulcanized rubber article reinforced with cellulose fiberscontaining at least 0.25% by weight of guanazole.

HOWARD M. BUCKWALTER. PHILLIP D. MONTGOMERY.

REFERENCES CITED UNITED STATES PATENTS Name Date DAlelio Feb. 20, 1945Number

1. THE METHOD OF IMPROVING THE RESISTANCE OF CELLULOSE FIBERS TO THEDETERIORATING EFFECTS OF HEAT AGING WHICH COMPRISES INCORPORATINGGUANAZOLE IN THE CELLULOSE FIBER IN AMOUNT OF AT LEAST 0.25% BY WEIGHT.